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20 Cards in this Set

  • Front
  • Back
Normal values for arterial and venous blood pH, and critical values
Arterial 7.35-7.45
Venous 7.32-7.42
Critical below 7.2 and above 7.6
Normal values for pCO2
35-45 mmHg
Normal values for pO2
83-108 mmHg
Normal values for arterial and venous TCO2
Arterial 22-29 mEq/L
Venous 23-30 mEq/L
Normal values for arterial and venous bicarb
Arterial 21-28 mEq/L
Venous 22-29 mEq/L
Normal values for base excess
+/- 3 mEq/L
Normal values for O2 saturation
95% or greater
Explain the principles of pH indicator electrode
Greater H+ on the outside of glass membrane makes the outside more + than inside of membrane and causes e- potential across membrane
As acidity increases e- potential increases
Explain the principles of calomel reference electrode
-Has Hg/HgCl2 paste cathode
- Takes into account the e- potential independent of potential due to H+ differences
Explain the principles of severinghaus CO2 electrode
Teflon permeable to CO2 gas, sample reacted with H2SO4
- CO2 reacts with water in bicarb buffer solution forming carbonic acid
- pH change is measured by pH electrode
Explain the principles of Clark pO2 electrode
O2 unites with H2 gass and reduces resistance
Explain specimen collection procedure
- Specimen of choice is heparinized arterial whole blood
- drawn in heparin-coated glass syringe
- don't excite patient (causes hyperventilation)
- apply tourniquet loosely
- mix specimen as soon as it is drawn
Common sources of blood gas analysis error
- improper mixing
- improper handling (exposing to air, not putting on ice)
- incorrect calibration or pH calibrator buffers are contaminated
- incorrect barometric pressure
- improper temp control (must be kept at exactly 37 C)
- Dirty sample chamber (protein buildup)
- Dirty electrode membranes (protein buildup)
- Damaged electrode membranes
Effects on sample from increased temp or failing to perform assay immediately
RBC's will catabolize glucose and cause falsely low pH and increased pCO2. pO2 will not be affected
Effects on sample from poor mixing and partial clotting
will cause falsely high pH (alkaline)
Effects on sample from exposure to ambient air
pCO2 will be falsely low, and pO2 will be high
Tricks used by the kidney to secrete more H+ when blood is to acidic
Excretion of ammonia and phosphates.
Excreted ammonia comes from modified glutamine
Effects of renal failure on pH, pCO2, pO2, and bicarb
-decreased pH (acidic)
- no direct effect on CO2 or O2
- low bicarbonate (bicarb is lost in urine)
Normal range for lactic acid
.5-1.9 mMol/L
at 4.5 mMol/L patient is considered to be in lactic acidosis
Importance of lactic acid levels in burn patients
-pO2 and pCO2 measurments are not reliable in a severely burned patient, they are falsely elevated due to decreased capillary resistance
- if lactic acid is increased then the physician knows that O2 is not being used by the body, and a transfusion is needed to increase O2 carrying capacity